Time-of-flight photoelectron momentum microscopy with 80–500 MHz photon sources: electron-optical pulse picker or bandpass pre-filter

Schönhense, G.; Medjanik, K.; Fedchenko, O.; Zymaková, A.; Chernov, S.; Kutnyakhov, D.; Vasilyev, D.; Babenkov, S.; Elmers, H.J.; Baumgärtel, P.; Goslawski, P.; Öhrwall, G.; Grunske, T.; Kauerhof, T.; von Volkmann, K.; Kallmayer, M.; Ellguth, M.; Oelsner, A.

doi:10.1107/S1600577521010511

Figure 5
Measurements using the bandpass pre-selection approach, recorded with the setup shown in Fig. 4

(b) using a narrow-bandwidth UV laser [hν = 6.4 eV; bandwidth < 0.5 meV; 80 MHz (https://www.ape-berlin.de/en/laser-arpes/)]. (a) Gaussian image showing the superposition of the upper edge of the entrance slit, the circular entrance aperture (half circle) and the grid in the field-aperture plane (vertical lines). (b) Momentum image showing the superposition of the grid in the backfocal plane of the objective lens with a surface state. (c, d) Linear increase of transit time versus entrance angle in the dispersive plane (c) and constant behavior in the perpendicular (non-dispersive) plane (d), measured in the HSA + ToF hybrid mode at a drift energy of 500 eV. (e, f) Data array recorded using the classical scanning mode of the HSA without ToF analysis: k_x–k_y momentum pattern of the Re(0001) Tamm state close to E_F (e) and E_B-versus-k_x section of the full photoemission paraboloid with diameter ∼1.25 Å⁻¹ at E_F (f). Second row, data recorded in the hybrid mode with E_pass = 200 eV and E_drift = 9 eV: (g, h) E_B-versus-k_x,y cuts through data arrays of Re(0001) and (i, j) same for 3 ML of Au on Re(0001). (k, l) Data array (width 880 meV) for 1T-TiTe₂, recorded in the hybrid mode at E_pass = 400 eV. (k) E_B-versus-k_y section as-measured (top) and after numerical elimination of the transit time spread (bottom). (l) k_x–k_y sections at E_B = 0.2 (top) and 0.4 eV (bottom). (m–o) Resolution measurements in the conventional scanning mode: intensity profiles of the Fermi edge of an Au film recorded at E_pass = 12 eV / W = 0.5 mm / T = 30 K (m), 8 eV / 0.4 mm / 30 K (blue) and 15 K (black) (n), and 8 eV / 0.2 mm / 15 K (o). Curves in (m,n,o) are to guide the eye; yellow arrows in (o) and the inset mark an intensity artifact slightly above E_F.

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 28| Part 6| November 2021| Pages 1891-1908

https://doi.org/10.1107/S1600577521010511

Open

access

Search IUCr Journals		doi		Advanced search
Author		volume	page